The basic mechanism of the reaction of hydrogen with carbon to form methane has been studied for relatively pure carbons1 and a detailed study .of the behaviour of chars made from brown coal has also been made.2 It has been shown that using carbons prepared by heating coals in dry nitrogen, the surface of such carbons becomes saturated with a hydrogen-carbon complex during pyrolysis. On subsequent reaction with hydrogen this complex is desorbed as a rapid initial impulse of methane. Once this initial desorption has ceased, the char shows a steady rate of reaction with hydrogen until at least 80% of the carbon has been gasified. It has long been assumed that the reactivity of a char or impure carbon to hydrogen is partly dependent on the source of carbon. However, it has recently been shown3 that for a brown coal char, prepared by heating the original coal in a stream of dry, oxygen-free nitrogen, the reactivity of the char is related exponentially to the temperature to which the char has been heated. Further, a char prepared for example at 950 and made to react at 750 was found to have a lower reactivity than one prepared at 750 and made to react at the same temperature. It is the purpose of this paper to show that chars or cokes prepared from a wide range of coals exhibit substantially the same reactivity to hydrogen when prepared at the same temperature. Experimental (a) Materials Six different coals, five from New South Wales and one from Western Australia, were pyrolysed in a silica retort in a stream of dry, oxygen-free nitrogen within the temperature range 720-725 and the temperature was maintained for 1 hr after the cessation of evolution of gas. The cokes and chars so produced were crushed and screened to a size of -7+ 14 B.S. Sieve. The types of coals used and the analyses, by the standard methods, of the chars produced are given in Table 1. Commercial dry hydrogen and oxygen-free dry nitrogen, from cylinders, were used for gas supplies. (b) Apparatus The above chars were treated with hydrogen in a tubular reactor in which the preheated reactant gas was allowed to flow through a fixed bed, 10 cm long, containing a weighed quantity, usually about 7-9 g of the char sample. The temperature, pressure, and flow rate were controlled